This invention pertains to a knob, such as an appliance knob, of a type having a polymeric part and a metal part, which is secured to the polymeric part and which has an outer surface that may be a finished, decorative, or indicia-bearing surface. This invention also pertains to a method of making such a knob.
Knobs of the type noted above are used widely for kitchen appliances, for entertainment devices, such as radios and television sets, and in diverse other applications. Commonly, the metal part of such a knob is an aluminum plate, which may be circular and which is secured adhesively to the polymeric part. Commonly, the outer surface of the metal part of such a knob may be finished, as by brushing or engine-turning, or may be decorated, as by enameling or anodizing, and may be an indicia-bearing surface.
U.S. Pat. No. 4,604,786 exemplifies a method of making a knob of the type noted above, wherein a machined apron of the metal part is removed except for two tabs, which are inserted into slots in the polymeric part, whereupon the tabs are bent inwardly to secure the metal part to the polymeric part.
This invention provides an improved knob, such as an appliance knob, of the type noted above. The improved knob has a polymeric body, which has a boss having an end face and having a wall. The polymeric body has a recess bordering the boss and having a floor, which the wall adjoins. The knob has a metal cup fitting over the boss. The metal cup has a plate covering the end face of the boss and a skirt bordering the wall of the boss and being unitary with the plate. The metal cup is secured to the polymeric body.
Preferably, the skirt has a unitary tab projecting from the skirt, into an associated slot in the floor, and being used to secure the metal cup to the polymeric body. The unitary tab may be one of two unitary tabs functioning similarly. In some contemplated embodiments, each unitary tab has a barbed portion, which coacts with the polymeric body to secure the metal cup to the polymeric body. In another contemplated embodiment, each unitary tab has a terminal portion, which is bent under the polymeric body to secure the metal cup to the polymeric body. In any contemplated embodiment, the plate may be also secured adhesively to the top of the central boss.
This invention also provides a method of making the improved knob. A polymeric material is molded to provide the polymeric knob, as described above. A metal sheet or a metal strip is stamped and drawn to provide the metal cup, as described above. The metal cup is secured, as described above, to the polymeric body.
Although polypropylene is preferred for the polymeric knob, another engineering polymer may be instead used. Although aluminum is preferred for the metal cup, stainless steel, chrome-plated steel, or any other suitable metal may be instead used.